1. Field of the Invention
The present invention relates to a conversion mechanism applicable to a high magnification dial gauge that magnifies the sliding amount of a spindle by a sector gear of which one end is supported by a case body in a turnable manner and displays the sliding amount using a turning amount of a pointer.
2. Description of the Related Art
A dial gauge that magnifies the sliding amount of a spindle by a sector gear of which one end is supported with a case body in a turnable manner and displays the sliding amount as a turing amount of a pointer has been known.
The dial gauge having such a magnification mechanism by the sector gear can be used for precision measurement and the like, because even only a slight slide of the spindle is detected as a change in the turing amount of the pointer.
For instance, a dial gauge 10 shown in FIG. 6 and FIG. 7 is known as a dial gauge having the sector gear.
The dial gauge 10 shown in FIG. 6 is formed including a body case 11 which holds a pointer 50 and a dial plate 51, and a spindle 20 which passes through the body case 11 and is supported by the body case in a slidable manner. When the spindle slides in the direction of the arrow A the pointer 50 turns through a sector gear 30 (shown in FIG. 7) and gives the amount of the slide of the spindle 20.
The inside of the dial gauge 10 has a configuration shown in FIG. 7, and the sector gear 30, a gear system 40, the pointer 50 and the dial plate 51 (shown in FIG. 7) are housed inside the body case 11.
The spindle 20 is a rodlike member extruding in a sliding direction, and is provided with a measuring point 21 on the end portion and a rack pin 22 which serves as a engaging portion projecting toward the outside of the diameter in the direction of the spindle 20 at the middle of the spindle 20.
The sector gear 30 is fixed in a rotatable manner on one end (upper left in FIG. 7) to the body case 11 by a sector shaft 32, and a gear portion 33 is formed on the other end.
An arm pin 34 which is an abutting portion to abut on the rack pin 22 of the spindle 20, thrusts through an arm 35 on the middle of the sector gear 30.
Though not shown in FIG. 7, the spindle 20 is resiliently biased so that the measuring point 21 protrudes from the body case 11 and the sector gear 30 is rotatably biased counterclockwisearound the sector shaft 32.
Thus, the rack pin 22 and the arm pin 34 remain in contact with each other, wherever the position in the sliding direction of the spindle 20 may be.
The gear system 40 is formed including a middle pinion 41 which engaged with the gear portion 33 of the sector gear 30, a large gear wheel 42 integrated with the middle pinion 41, and a center pinion 43 which is engaged with the large gear wheel 42 and turns the shaft of the pointer 50.
The slide of the spindle 20 in the direction A is converted into the clockwise rotation pivoting on the sector shaft 32 of the sector gear 30 through the rack pin 22 and the arm pin 34. After that, the rotation of the sector gear 30 in the clockwise direction turns the middle pinion 41 and the large gear 30 in the clockwise direction through the gear portion 33, and the pointer 50 turns clockwise through the center pinion 43 which is meshed with the large gear wheel 42.
Similarly, when the spindle 20 slides in the A' direction, the pointer 50 turns counterclockwise.
In a conversion system of a dial gauge having the configuration, the sector gear 30 is provided with the arm 35 fixed on the sector gear 30 in a rotatable manner with a machine screw 35A, and an eccentric cam 36 abutting to the side surface of the arm 35 and controlling the turning of the arm 35 as shown in FIG. 8 and FIG. 9. The arm pin 34 is protruded from the arm 35.
The reason of the sector gear having such a configuration is to prevent the effect of excessive moment on a connecting portion 37 of the arm pin 34 by the force along the direction of B caused by the rack pin 22, through minimizing the protrusion size D of the arm pin 34.
However, in the sector gear 30 having such a configuration, the arm 35 and the eccentric cam 36 must be separately provided on the sector gear 35, thus making a disadvantage of cost for parts due to the increase of the number of parts.
Moreover, when the sector gear 30 is housed in the body case 11, the dimension R that is a distance between the sector shaft 32 and the arm pin 34 must be adjusted, thus making another disadvantage of increasing in complexity of assembling of the dial gauge 10.
On the other hand, in a case that an object is measured with the dial gauge 10, comparing with a reference block, when the measuring point 21 is abutted to the reference block, the turning angle of the pointer 50 does not always match with the zero position on the dial plate 51.
Therefore, hitherto, the dial plate 51 has been made turnable from outside of the body case 11 as shown in FIG. 6, and the measurement is carried out after the zero position of the dial plate is adjusted to the turning angle of the pointer 50 (in the C-direction in FIG. 6).
However, there arises another disadvantage that in some Turing angles of the pointer 50, readout of numbers on the dial plate 51 becomes difficult.
Further, when the dial plate 51 is turned, a deviation between a dial range of the dial plate 51 and a turning range of the pointer 50 is sometimes created. In this case, the pointer 50 possibly indicates a point A where there is no mark on the dial plate 51 so that the turning amount of the pointer 50 can not be read out from the dial plate 51.
It is the first object of the present invention to present a conversion mechanism of the dial gauge to decrease the number of parts and simplify the assembling.
The second object of the present invention is to present a conversion mechanism of the dial gauge to enable to change a turning angle of the pointer without changing a position of the measuring point in the sliding direction.